The conversion of motor or engine output power into required output torque and speed for vehicular motivation is accomplished by a transmission that usually includes some arrangement of gears and/or belt drives. Further, these elements are so arranged as to change speed and torque at fixed ratios such that transmissions are referred to by the number of fixed ratios they are capable of providing in the forward driving direction. The average automotive transmission has 4 speeds but there are also 5, 6 and 7 speed automotive transmissions and up to 32 speeds or more for truck transmissions. Other configurations of transmissions are applicable for specialty vehicles, off-road vehicles and equipment, agricultural vehicles and equipment, and marine vessels. The ability to change from one ratio to another ratio can be fully manual, automated manual, semi-automatic, or automatic. The ratios are designed to provide the appropriate torque and speed for the desired acceleration and velocity of the vehicle. So that, a first ratio of an automobile will provide high torque at a low vehicle velocity as would be required when starting from rest. The high torque is necessary to accelerate the vehicle from rest. As the vehicle increases in velocity, a second speed ratio would be required to provide more speed to the driving wheels to continue the acceleration to a higher vehicle velocity. The amount of torque required diminishes as the vehicle velocity increases as the torque requirement is significantly less to sustain a moving mass. A third, fourth, and so on ratio continue the process to achieve the desired vehicle velocity. The same is true for trucks but with many more ratios required due to the substantially greater mass of the vehicle and payload. The specific ratios, the incremental ratio steps between ratios, the ratio range (lowest gear/highest gear), the shift quality from one ratio to another ratio, the efficiency of the transmission and the cost are all factors for consideration when advancing conventional transmission technology.
The transition of changing from one ratio to another ratio in truck transmissions is operator intensive due to the large number of necessary ratios. The total mass of the vehicle including its payload requires the operator to be very active at changing ratios, particularly from rest up to some intermediate vehicle velocity. Often several ratio changes are required from rest to only 10 mile per hour (mph) vehicle velocity. The demand on the motor or engine for steep grades, both uphill and downhill requires transmissions with a large number of ratios to meet these demanding conditions for trucks. The greater the number of ratios available the more ratio selection options the operator has available to match vehicle velocity and desired acceleration to the road and load conditions. Unfortunately, the greater the number of ratios in a transmission, the more complex it is, the larger and heavier it is, and the more expensive it is.
It is desirable to advance transmission technology to deliver overall vehicle improved fuel efficiency which correlates to a reduction in engine emissions, reduce the actual cost of manufacturing and maintaining a transmission, and provide the desired overall vehicle performance including but not limited to: launch acceleration, shift quality, cruise, passing, hill climb and descent.